In the attempt to evaluate what is the role of cerebroside synthesis in developing brain, I am proposing two approaches; characterization of rat brain subcellular fractions that are relatively enriched in UDP-galactose:ceramide galactosyltransferase over UDP-glucose:ceramide glucosyltransferase, and solubilization and characterization of the galactosyltransferase, particularly with respect to the role of lipid in the expression of the enzymatic activities. The first approach attempts to answer the question as to whether the galactosyltransferase rich fraction might be derived from neuronal components and as to what are the interrelationships among such subcellular fractions and mature myelin. The aim of the second approach is to better define the exogenous lipid effects on UDP-galactose: ceramide galactosyltransferase by eliminating the ambiguity inevitably associated with the studies using insoluble, membrane-bound enzymes. Thus, the results of these projects should provide the basic information necessary to eventually examine the fundamental questions posed above.